The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art to the presently claimed invention, nor that any of the publications specifically or implicitly referenced are prior art to that invention.
Publications and other materials including patents and patent applications used to illuminate the specification are hereby incorporated by reference.
The exendins are peptides that are found in the venom of the Gila-monster, a lizard found in Arizona. Exendin-3 (SEQ ID NO: 1) is present in the venom of Heloderma horridum, and exendin-4 (SEQ ID NO: 2) is present in the venom of Heloderma suspectum (Eng et al, J. Biol. Chem., 265:20259-62 (1990); Eng, et al, J. Biol. Chem., 267:7402-05 (1992)). The exendins have some sequence similarity to several members of the glucagon-like peptide family, with the highest homology, 53%, being to GLP-1(7-36)NH2 (Goke et al, J. Biol. Chem., 268:19650-55 (1993)). GLP-1(7-36)NH2 (SEQ ID NO: 3) is also known as proglucagon(78-107), or simply the shorthand “GLP-1,” which is used interchangeably with GLP-1(7-36)NH2 throughout this application. The sequences of exendin-3, exendin-4 and GLP-1 are shown in FIG. 1. GLP-1 has an insulinotropic effect, stimulating insulin secretion from pancreatic beta-cells; GLP-1 also inhibits glucagon secretion from pancreatic alpha-cells (Ørskov et al, Diabetes, 42:658-61 (1993); D'Alessio et al, J. Clin. Invest., 97:133-38 (1996)). GLP-1 is reported to inhibit gastric emptying (Willms et al, J. Clin Endocrinol Metab, 81(1):327-32 (1996); Wettergren et al, Dig Dis Sci, 38(4):665-73 (1993)), and gastric acid secretion (Schjoldager et al, Dig Dis Sci, 34(5):703-8 (1989); O'Halloran et al, J Endocrinol, 126(1):169-73 (1990); Wettergren et al, Dig Dis Sci, 38(4):665-73 (1993)). GLP-1(7-37), which has an additional glycine residue at its carboxy terminus, also stimulates insulin secretion in humans (Ørskov et al, Diabetes, 42:658-61 (1993)).
A transmembrane G-protein adenylate-cyclase-coupled receptor believed to be responsible for the insulinotropic effect of GLP-1 has been cloned from a beta-cell line (Thorens, Proc. Natl. Acad. Sci. USA, 89:8641-45 (1992), hereinafter referred to as the “cloned GLP-1 receptor.” Exendin-4 is reportedly a potent agonist at GLP-1 receptors on insulin-secreting betaTC1 cells, at dispersed acinar cells from guinea pig pancreas, and at parietal cells from stomach; the peptide is also reported to stimulate somatostatin release and inhibit gastrin release in isolated stomachs (Goke et al, J. Biol. Chem., 268:19650-55 (1993); Schepp et al, Eur. J. Pharmacol., 69:183-91 (1994); Eissele et al, Life Sci., 55:629-34 (1994)). Exendin-3 and exendin-4 were found to be GLP-1 agonists in stimulating cAMP production in, and amylase release from, pancreatic acinar cells (Malhotra et al, Regulatory Peptides, 41:149-56 (1992); Raufman et al., J. Biol. Chem., 267:21432-37 (1992); Singh et al, Regul. Pept., 53:47-59 (1994)). Based on the insulinotropic activities of exendin-3 and exendin-4, their use has been proposed for the treatment of diabetes mellitus and the prevention of hyperglycemia (U.S. Pat. No. 5,424,286).
In contrast to the full-length exendins, truncated exendin peptides such as exendin(9-39), a carboxyamidated molecule, and fragments 3-39 through 9-39 of exendin have been reported to be potent and selective antagonists of GLP-1 (Goke et al, J. Biol. Chem., 268:19650-55 (1993); Schepp et al, Eur. J. Pharm., 269:183-91 (1994); Montrose-Rafizadeh et al, Diabetes, 45(Suppl. 2):152A (1996)). Exendin(9-39), the sequence of which is shown in FIG. 1 as SEQ ID NO: 4, reportedly blocks endogenous GLP-1 in vivo, resulting in reduced insulin secretion (Wang et al, J. Clin. Invest., 95:417-21 (1995); D'Alessio et al, J. Clin. Invest., 97:133-38 (1996)). Exendins and exendin(9-39) bind to the cloned GLP-1 receptor (Fehmann et al, Peptides, 15(3):453-6 (1994); Thorens et al, Diabetes, 42(11):1678-82 (1993)). In cells transfected with the cloned GLP-1 receptor, exendin-4 is an agonist, i.e., it increases cAMP, while exendin(9-39) is an antagonist, i.e., it blocks the stimulatory actions of exendin-4 and GLP-1.
Exendin(9-39) is also reported to act as an antagonist of the full length exendins, inhibiting stimulation of pancreatic acinar cells by exendin 3 and exendin 4 (Raufman et al, J. Biol. Chem., 266:2897-902 (1991); Raufman et al., J. Biol. Chem., 266:21432-37 (1992)). Exendin(9-39) is said to inhibit the stimulation of plasma insulin levels by exendin 4, and inhibits the somatostatin release-stimulating and gastrin release-inhibiting activities of exendin-4 and GLP-1 (Kolligs et al, Diabetes, 44:16-19 (1995); Eissele et al., Life Sciences, 55:629-34 (1994)).
Agents which serve to delay gastric emptying have found a place in medicine as diagnostic aids in gastro-intestinal radiologic examinations. For example, glucagon is a polypeptide hormone which is produced by the alpha cells of the pancreatic islets of Langerhans. It is a hyperglycemic agent which mobilizes glucose by activating hepatic glycogenolysis. It can to a lesser extent stimulate the secretion of pancreatic insulin. Glucagon is used in the treatment of insulin-induced hypoglycemia when administration of glucose intravenously is not possible. However, as glucagon reduces the motility of the gastrointestinal tract it is also used as a diagnostic aid in gastrointestinal radiological examinations. Glucagon has also been used in several studies to treat various painful gastro-intestinal disorders associated with spasm. Daniel et al, Br. Med. J., 3:720 (1974) reported quicker symptomatic relief of acute diverticulitis in patients treated with glucagon compared with those who had been treated with analgesics or antispasmodics. A review by Glauser et al., J. Am. Coll. Emergency Physns, 8:228 (1979) described relief of acute esophageal food obstruction following glucagon therapy. In another study glucagon significantly relieved pain and tenderness in 21 patients with biliary tract disease compared with 22 patients treated with placebo (Stower et al, Br. J. Surg., 69:591-2 (1982)).
Methods for regulating gastrointestinal motility using amylin agonists are described in International Application No. PCT/US94/10225, published Mar. 16, 1995.